Interconnection of control units, sensors, and actuators, using such a communication system, i.e., bus system, has increased and may have even drastically increased in the past few years with the construction of modern motor vehicles, in machine construction, in the machine tool industry in particular, as well as in automation and other industrial applications. Synergistic effects as a result of the distribution of functions to a plurality of control units may thus be achieved. This is referred to as a distributed system. Communication among different nodes takes place increasingly via at least one bus or at least one bus system. Communication traffic on the bus system, access and receiving mechanisms, as well as error processing are regulated via a protocol.
One approach for doing so is time-controlled communication in time-controlled bus systems. Such time-controlled communication systems are based on cyclical transmission of messages in a fixed time pattern. The sequence for this time pattern is derived from a freewheeling timer or time master in the system, which specifies this global time for the time-controlled bus system. One example of such a time-controlled bus system is the time-controlled CAN (Controller Area Network) corresponding to ISO Standard 11898-4, known as TTCAN or time-triggered controller area network.
In the TTCAN and other time-controlled bus systems, such as FlexRay, communication rounds (for example, basic cycle) are formed; such time-controlled communication systems, such as TTCAN or FlexRay, are thus essentially based on time-controlled periodic communication, which is timed by a main timing node, referred to as the time master, with the help of a time reference message or reference message for short. The period to the next reference message is referred to as the basic cycle, which is subdivided into a predefinable number of time windows and includes the cycle time of the time-controlled bus system.
Control units in such time-controlled communication systems may have direct bus access for exchanging application messages. These messages must be provided in a timely manner in the above-described time-controlled bus systems. This requirement may be met, for example, by using a time-controlled operating system, such as OSEK. The time perception of the operating system, an OSEKtime-compatible OS, for example, is then derived from the above-described global time (GT).
In such interconnected systems having time-controlled communication, sensors and actuators are also directly connected, i.e., the logic of the sensor or actuator also assumes the function of participating in the bus traffic.
The special behavior, the time behavior in particular, of the bus system when sensors and actuators are used is not specifically explained in the related art. This means that the time-controlled behavior of such bus systems is not directly assumed by the sensor or actuator, thereby resulting in time uncertainties with reference to the timeliness of the measurement data in particular in the case of sensors in addition to the maximum allowable phase rotation normally described in the sensor specification, i.e., a time shift within the signal processing.